While the practice of splicing foreign DNA into food crops has become common in corn and soy, few companies or researchers have dared to apply genetic engineering to plants that provide an essential strut of the U.S. economy, trees.

But that will soon change. Two industry giants, International Paper Co. and MeadWestvaco Corp., are planning to transform plantation forests of the southeastern United States by replacing native pine with genetically engineered eucalyptus, a rapidly growing Australian tree that in its conventional strains now dominates the tropical timber industry.

The companies' push into genetically modified trees, led by their joint biotech venture, ArborGen LLC, looks to overcome several hurdles for the first time. Most prominently, they are banking on a controversial gene splice that restricts trees' ability to reproduce, meant to allay fears of bioengineered eucalyptus turning invasive and overtaking native forests.

If such a fertility control technology -- which has come under fire in farming for fear seed firms will exploit it -- is proven effective, it could open the door to many varieties of wild plants, including weedy grasses, to be genetically engineered for use in energy applications like biomass and next-generation biofuels without fear of invasiveness.

The use of such perennial plants -- so named because, unlike annual farm crops, they live and grow for many years -- has long interested business and government, including the Energy Department, which has collaborated with ArborGen. The plants, which include many grasses targeted for cellulosic ethanol, can be harvested when needed and, given their hardiness, grow on marginal land.

Yet many questions remain about the effectiveness of the fertility system used by ArborGen, which, according to leading scientists, has never been rigorously studied in multiyear trials to prove that it can effectively control plants' spread. More research must be conducted before such systems are relied upon to restrict pollen and seed spread, they say.

Despite these calls, ArborGen has been seeking government deregulation of its eucalyptus, which is primarily engineered to resist freezing temperatures, since 2008. If successful, ArborGen would likely revolutionize the timber industry and the Southern landscape by becoming the first company to roll out bioengineered trees on a massive scale, observers say.

In its rosiest scenarios, growers using ArborGen's presumably expensive seeds would see huge gains in productivity and become the preferred tree stock for a new generation of bioenergy refineries. The South would become the new Appalachia; timber would serve as its coal. Inklings of such progress have already arisen, including recent word that the German utility RWE AG would build the world's largest wood-pellet plant in Georgia to supplement its coal habits.

By adopting eucalyptus as a tree stock, the United States would simply be catching up with countries like Brazil, which has leveraged vast tree plantations in recent decades to pivot from a net wood importer to an exporter. While the South saw a rise in pine plantations during this time, pine cannot compete with eucalyptus for sheer growth rate, the company says.

"The United States is behind the game on this," said Les Pearson, ArborGen's director of regulatory affairs. "Lots of countries around the world have been growing eucalyptus for many decades."

Indeed, primarily because of competition from South America, demand for traditional American tree pulp has gone slack. This sagging industry could allow up to 10 million acres in the Southeast to be repurposed for fast-growing eucalyptuses, according to corporate estimates.

But it still remains unclear if the nascent bioenergy industry will be enough to make up for demand lost to Brazilian plantations, said Curtis Seltzer, a timber consultant who has studied ArborGen and calls its trees a "game changer."

"It's not clear to me that biomass will pick up the slack for the traditional markets [as they] ebb," Seltzer said. "But it could."

Even given government incentives and a price on carbon, however, ArborGen must satisfy concerns from regulators and environmental groups that its engineered trees will not, especially when gifted with the ability to resist cold, spread untrammeled through forests.

Pollen problems

At its most basic, life is about reproduction. And the species' struggle to adapt and survive can make attempts to control the fertility of plants difficult, according to Steve Strauss, a tree geneticist at Oregon State University who has also consulted with ArborGen.

ArborGen relies on what has been the most popular system for restricting plant pollen, which uses a bacterial gene to produce a toxic enzyme called barnase that slices apart genetic material in a cell, causing death. Through genetic trickery, the enzyme is only produced in the pollen-spreading parts of the tree, destroying its ability to reproduce -- at least most of the time.

Given the number of trees that will be produced, there will likely be enough genetic instability to allow a very small number of the freeze-tolerant eucalyptuses to reproduce, Strauss said. Rather than an absolute containment system, barnase should be thought of as a mitigation strategy, he added.

A tiny number of seedlings are almost assured to escape from the eucalyptus plantations, Strauss said. But since the trees, in his evaluation, are unlikely to prove invasive, there should be little cause for alarm.

"When you talk about trees, storms happen, wind blows," he said. "The containment is not absolute. There is the chance of some spread. Is it likely to become an invasive weed? Seems unlikely to me."

Until now, only two of ArborGen's experimental eucalyptus stations have been allowed to flower, and the company has reported little in the way of pollen production in the trees. It is now seeking to greatly expand the number and location of trees allowed to flower to 28 sites totaling 330 acres scattered across seven states. The Agriculture Department issued a draft approval of the expansion, subject to public comment, earlier this month.

The modified eucalyptus trees are already planted at most of these sites, and as they approach sexual maturity, ArborGen has been forced to pluck the trees' flowers or cut them down completely, causing millions of dollars in lost research, said Nancy Hood, ArborGen's public affairs director.

This test acreage is fairly small, hardly the equivalent of a full-scale commercial planting, as some environmental groups have accused. (For comparison, there are more than 32 million acres of pine plantation in the South.) However, ArborGen has confessed that it hopes USDA will deregulate the trees by the time the cohort reaches harvest age -- around seven years or so -- allowing the resulting pulp to be sold.

Many biotech researchers are supportive of the expanded experimental permit, which will allow more complete studies of the fertility containment system. While ArborGen has released little in the way of peer-reviewed research so far, it will publish barnase results this year, said Maud Hinchee, ArborGen's chief technology officer.

Such data would be a welcome change. While barnase's mechanism is well documented -- and approved for use in domesticated crops like rapeseed -- its effectiveness has barely been studied, according to an analysis written by Strauss in 2007.

"There does not seem to have been any serious field studies, in any crop, sufficient to estimate the operational effectiveness of containment genes," Strauss wrote. "Until many such studies are published, it would be unwise to assume that genes can be fully and safely contained in the near future."

Decisions to deregulate any wild GM plant like the eucalyptus must take into account this lack of research, said Hong Luo, a molecular biologist at Clemson University who has developed a gene containment system for another wild plant, turfgrass. His team recently completed a one-year study of the system's effectiveness, he said, but more research is needed.

"There haven't been really too much studies of what would be impact of transgene escape from perennials," he said. "We will be cautious in this respect."

It remains to be seen how the public will react to the concept of GM forest trees. But as researchers point out, people have already embraced some engineered trees that have no pollen controls. Almost all of the papaya trees in Hawaii are genetically engineered to resist the devastating ringspot virus, and similar efforts are under way to save the American chestnut, which has been nearly eradicated by fungal disease.

However, the inability to promise 100 percent containment could delay the development of bioengineered plants that carry even slight risks of invasiveness. But such foolproof systems will come, Strauss predicted.

"I do believe we can produce absolute containment," he said. "We will be able to do that, I believe, in 10 years. But it's not proven yet."

Australian invaders

The unproven nature of ArborGen's fertility controls is concerning largely because they will be used to introduce a robust, foreign tree, conservation groups say. The timber industry has long dreamed of importing eucalyptus into the South, mimicking Brazil's success, where plantations transformed the country -- at some environmental toll -- from a timber importer to an exporter within decades.

Previous domestic efforts to establish the tree in the South, which came to a peak in the early 1980s, failed as winter freezes scythed dead swaths through experimental plantations. Only in Florida have the trees survived, though they have only been used in only limited ways, mostly for mulch. All efforts to move the tree into more temperate conditions have failed, until now.

Thanks to a plant gene that it licensed from Mendel Biotechnology, a prime R&D contractor with Monsanto Co., ArborGen's freeze-tolerant eucalyptuses have been grown in much colder conditions up into the Carolinas. (ArborGen has many connections to Monsanto, starting with its CEO, Barbara Wells, who worked at the seed giant for 18 years.) Mendel's regulatory gene controls the expression of other genes that influence cold resistance, and its use represents the state of the art in plant biotech.

But in opening the door to the plant's cultivation, far more scrutiny is needed as to how eucalyptus will behave when grown in bulk, said Doria Gordon, a senior ecologist at the Nature Conservancy.

"My concern is about invasiveness. Not that it is a GMO, per se," Gordon said. "The concern is, what threat is it to Florida's natural area and to the Southeast's natural areas?"

Last year, Gordon, who also works at the University of Florida, evaluated one of the two species used to breed ArborGen's hybrids, Eucalyptus grandis, also known as the rose gum. The tree had previously turned invasive in South Africa, Gordon found, which led her to conclude that the tree carried a risk of turning invasive in the South, as well.

Gordon serves on a panel that evaluates the invasive risk of plants in Florida, and last year, the panel classified the rose gum as a possible invader. Only a few variants of the tree can be grown, it said, and only with strict management practices, including harvesting within six months of the onset of flower production -- much sooner than a forest plantation would like.

Though the rose gum carries an invasive risk, ArborGen's trees are an unknown quantity, Gordon said. Given the uncertainty involved, however, the Nature Conservancy has recommended to USDA that ArborGen be allowed fewer acres and trees to flower, and none in Florida, she said. The draft permit approved by USDA would allow flowering in 10 sites across the state.

"We don't know if it could become more invasive over time," she said. And until then, "it would be logical to me to not do those trials in Florida."

It is not irrational to fear invasiveness in eucalyptus, said Dan Binkley, a forest ecologist at Colorado State University. However, the rose gum appears to take on weedy traits only in arid regions like South Africa, where it can leverage its tremendous water efficiency. The South is far moister by comparison.

Even in Florida, the eucalyptus has proved to be somewhat delicate, ArborGen's Pearson added.

The tree "does not exist outside of the planted environment," he said. And in the closed confines of a plantation, "you need to manage these things very carefully to let them survive and thrive."

'More Wood. Less Land'

While he would like to see more data on the water use and fire impacts of eucalyptus plantations, Binkley understands the tree's allure, he said.

Unlike the pine trees used in Southern plantations -- which have quietly helped displace tobacco in the region's economy -- eucalyptus can deploy a full canopy of leaves within a few years. It is greedy for carbon, and within 27 months can grow to 55 feet in height.

The ultimate benefit of eucalyptus plantations would be the ability to grow more wood on less land, ArborGen's Hinchee said. (Not coincidentally, the firm's motto is "More Wood. Less Land.") Forests are continuously lost to development in the South, and natural hardwood acres have become harder to harvest. Increased productivity would have benefits "through the whole economic chain," she said.

Similar claims have been made for the practice of forest plantations as a whole, which remains controversial despite its ubiquity in the South, and little data exists to verify the claims.

In the end, if the United States seriously pursues bioenergy from plants, the country will face a choice of drawing that power more from trees that are treated like crops, or from grasses, which can behave far more invasively, Strauss said.

"If we're going to rely on biofuels as a significant part of a diverse portfolio of renewable technology," then harvesting trees is the best way to go, he said. "There's a lot of marginal land that could be used."